The overall purpose of this proposal is to examine the role of the limbic system in hypothalamic aggression. The first phase of the research proposal attempts to determine how the limbic system and related structures modulate quiet biting attack elicited by electrical stimulation of the hypothalamus. The principal paradigm involves presentation of paired trials of single (hypothalamic) and dual (limbic plus hypothalamic) stimulation. Differences in response latency between paired trials of single and dual stimulation provide the basis for determining the effects of limbic stimulation upon hypothalamic aggression. The limbic structures thus far considered include the hippocampus, amygdala, septal area, cingulate gyrus, pyriform cortex, and prefrontal cortex. In this proposal structures to be studied include the substantia innominata and mammillary bodies. In a second and related part of the project, we will attempt to identify more precisely how the limbic system produces its modulating effects upon atttack behavior by determining its actions upon the sensory and motor components of the attack reflex. A third part of the proposal is designed to identify the origin and distribution of the efferent connections of the septal area - a region known to be important to the control of aggressive behavior - in the cat and monkey. Other experiments will employ 2-DG radioautography in order to identify the functional relationships of the limbic system and hypothalamus. A final phase will atttempt to determine the neurophysiological relationships: (1) between hypothalamic attack sites and neurons in the limbic system and midbrain; (2) between limbic structures and their target nuclear groups as revealed by 2-DG radioautography; and (3) between the substantia innominata and its target neurons in the amygdala.